1/52+49/52×51+49×48/52×51×50+.+49×...×1/52×...×3=?1/52+49/52×51+49×48/52×51×50+.+49×...×1/52×...×=?1/52+49/52×51+49×48/52×51×50+......+49×...×1/52×...×3=?
来源:学生作业帮助网 编辑:六六作业网 时间:2024/12/23 09:01:33
1/52+49/52×51+49×48/52×51×50+.+49×...×1/52×...×3=?1/52+49/52×51+49×48/52×51×50+.+49×...×1/52×...×=?1/52+49/52×51+49×48/52×51×50+......+49×...×1/52×...×3=?
1/52+49/52×51+49×48/52×51×50+.+49×...×1/52×...×3=?
1/52+49/52×51+49×48/52×51×50+.+49×...×1/52×...×=?
1/52+49/52×51+49×48/52×51×50+......+49×...×1/52×...×3=?
1/52+49/52×51+49×48/52×51×50+.+49×...×1/52×...×3=?1/52+49/52×51+49×48/52×51×50+.+49×...×1/52×...×=?1/52+49/52×51+49×48/52×51×50+......+49×...×1/52×...×3=?
原式=51×50/52×51×50+50×49/52×51×50+49×48/52×51×50+48×47/52×51×50+.2×1/52×51×50=﹙51×50+50×49+49×48+48×47+.+2×1﹚/52×51×50
因为 1×2=1×2×3×1/3 2×3=1/3×﹙2×3×4-1×2×3﹚ 3×4=1/3×﹙3×4×5-2×3×4﹚
4×5=1/3×﹙4×5×6-3×4×5﹚.51×50=1/3×﹙50×51×52-49×50×51﹚
所以1×2+2×3+3×4+4×5+.+50×51=1/3×(1×2×3+2×3×4-1×2×3+3×4×5-2×3×4...) =
1/3×50×51×52
所以原式=1/3
不知道我计算过程有没有失误.